1. Field of the Invention
The present invention relates to a method for producing cerium dioxide (CeO2) nanopowder by flame spray pyrolysis and a cerium dioxide nanopowder produced by the method. More specifically, the present invention relates to: a method for producing a cerium dioxide nanopowder by flame spray pyrolysis, which is a dry process for the large-scale production of high-purity composite powders in a continuous manner, wherein the concentration of a raw material and the kind of a solvent are suitably selected to allow the cerium dioxide nanopowder to have a uniform particle size distribution and a small particle size, and a cerium dioxide nanopowder produced by the method.
2. Description of the Related Art
Cerium dioxide, also called ceria or cerium oxide, has a cubic crystal structure and is one of the most applicable and attractive rare earth metal oxides. Cerium dioxide can be utilized in various industrial fields, including fuel cells, insulators, UV screening agents as high refractive index materials, abrasives, gas sensors, high-temperature and oxidation resistant materials, etc. In addition, cerium dioxide is used as a ternary catalyst of an automotive muffler, a catalytic activator or a catalyst support.
The performance of cerium dioxide as a catalyst is dependent on its size. Nanometer sized cerium dioxide is expected to have effects, such as shift of Raman-allowed modes, lattice expansion, blue shift of UV absorption spectra, increased electronic conductivity and fast oxidation rate of carbon monoxide.
Numerous methods have been attempted to produce ceria nanopowders, for example, hydrothermal synthesis, precipitation, solid-phase combustion, mechano chemical processing, sol-gel processing, gas condensation, and high-frequency heating.
Although gas-phase synthesis is known to be economically advantageous in the production of nanoparticles, it fails to control the size of nanoparticles and have great difficulty in the production of multi-component materials other than one-component materials. For these reasons, gas-phase synthesis is currently utilized to produce low-priced nanoparticles rather than to produce high value-added ceramic nanoparticles despite its cost advantage. It is widely known that liquid-phase synthesis enables the production of spherical nanoparticles in a size-controllable manner. Liquid-phase synthesis can be utilized in many applications, but it incurs considerable production costs. Since subsequent heat treatment is essentially involved in the production of ceramic particles by liquid-phase synthesis, the problems of powder aggregation and increased particle size are inevitable, leaving room for improvement.
In the case of conventional methods for producing nanoparticles of cerium dioxide by flame spray pyrolysis, suitable solvents, such as distilled water, are used to dissolve raw materials. In this case, the use of water makes the cerium dioxide particles non-uniform in size distribution and as large as 20 nm in size.
Under these circumstances, there is a need to develop a technique for producing nanoparticles of cerium dioxide with a uniform size distribution.